Post Images: add image exclusion via CSS class and filter

[kraftbj]

Fixes #47054

Proposed changes:

• Add jetpack-ignore-thumbnail CSS class support to Jetpack_PostImages — any <img> tag with this class (or any block with this class in "Advanced > Additional CSS class") is skipped during image discovery
• Add jetpack_postimages_exclude_image filter for programmatic exclusion — developers can hook in to exclude images by URL pattern, dimensions, or other metadata
• Both mechanisms apply at the Jetpack_PostImages level (from_html and from_blocks), so all consumers benefit: Related Posts, Open Graph tags, and anything else that relies on this class for image selection

Other information:

• Have you written new tests for your changes, if applicable?
• Have you checked the E2E test CI results, and verified that your changes do not break them?
• Have you tested your changes on WordPress.com, if applicable (if so, you'll see a generated comment below with a script to run)?

Jetpack product discussion

Does this pull request change what data or activity we track or use?

No.

Testing instructions:

• Create a post with two images and no featured image set
• Add the CSS class jetpack-ignore-thumbnail to the first image:
  • Block editor: Select the image block → open the "Advanced" panel in the sidebar → add jetpack-ignore-thumbnail to "Additional CSS class(es)"
  • Classic editor: Add class="jetpack-ignore-thumbnail" to the <img> tag in the HTML view
• Verify that Related Posts (and/or Open Graph meta tags) use the second image instead of the first
• Alternatively, test the filter by adding this to a plugin or functions.php:

add_filter( 'jetpack_postimages_exclude_image', function( $exclude, $image ) {
    if ( str_contains( $image['src'], 'qr-code' ) ) {
        return true;
    }
    return $exclude;
}, 10, 2 );

Changelog

• Generate changelog entries for this PR (using AI).

[github-actions]

Are you an Automattician? Please test your changes on all WordPress.com environments to help mitigate accidental explosions.

• To test on WoA, go to the Plugins menu on a WoA dev site. Click on the "Upload" button and follow the upgrade flow to be able to upload, install, and activate the Jetpack Beta plugin. Once the plugin is active, go to Jetpack > Jetpack Beta, select your plugin (Jetpack), and enable the related-posts-image-filter branch.
• To test on Simple, run the following command on your sandbox:

bin/jetpack-downloader test jetpack related-posts-image-filter

Interested in more tips and information?

• In your local development environment, use the jetpack rsync command to sync your changes to a WoA dev blog.
• Read more about our development workflow here: PCYsg-eg0-p2
• Figure out when your changes will be shipped to customers here: PCYsg-eg5-p2

[github-actions]

Thank you for your PR!

When contributing to Jetpack, we have a few suggestions that can help us test and review your patch:

• ✅ Include a description of your PR changes.
  
• ✅ Add a "[Status]" label (In Progress, Needs Review, ...).
  
• ✅ Add testing instructions.
  
• ✅ Specify whether this PR includes any changes to data or privacy.
  
• ✅ Add changelog entries to affected projects
  

This comment will be updated as you work on your PR and make changes. If you think that some of those checks are not needed for your PR, please explain why you think so. Thanks for cooperation 🤖

---

Follow this PR Review Process:

1. Ensure all required checks appearing at the bottom of this PR are passing.
2. Make sure to test your changes on all platforms that it applies to. You're responsible for the quality of the code you ship.
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---

Jetpack plugin:

The Jetpack plugin has different release cadences depending on the platform:

• WordPress.com Simple releases happen as soon as you deploy your changes after merging this PR (PCYsg-Jjm-p2).
• WoA releases happen weekly.
• Releases to self-hosted sites happen monthly:
  • Scheduled release: March 3, 2026
  • Code freeze: March 3, 2026

If you have any questions about the release process, please ask in the #jetpack-releases channel on Slack.

[Copilot]

Pull request overview

This PR adds image exclusion capabilities to Jetpack_PostImages, allowing users to prevent specific images from being selected for Related Posts thumbnails, Open Graph tags, and other features. The implementation provides two exclusion mechanisms: a CSS class (jetpack-ignore-thumbnail) and a programmatic filter (jetpack_postimages_exclude_image).

Changes:

• Added CSS class-based exclusion (jetpack-ignore-thumbnail) that works in both from_html() and from_blocks() methods
• Implemented jetpack_postimages_exclude_image filter for programmatic image exclusion with comprehensive documentation
• Added test coverage for both CSS class exclusion and filter-based exclusion in HTML and block contexts

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
projects/plugins/jetpack/class.jetpack-post-images.php	Core implementation of CSS class check and filter hook in from_html() and from_blocks() methods with detailed filter documentation
projects/plugins/jetpack/tests/php/media/Jetpack_PostImages_Test.php	Comprehensive test coverage for CSS class exclusion in HTML/blocks and filter-based exclusion
projects/plugins/jetpack/changelog/related-posts-image-filter	Changelog entry describing the enhancement

[jp-launch-control]

Code Coverage Summary

Coverage changed in 1 file.

File	Coverage	Δ%	Δ Uncovered
projects/plugins/jetpack/class.jetpack-post-images.php	333/544 (61.21%)	0.47%	1 ❤️‍🩹

Full summary · PHP report · JS report